Spin tunnel magneto-resistance effect type magnetic sensor and production method thereof

ABSTRACT

A magnetic sensor utilizing a spin tunnel magneto-resistance effect (TMR), comprising a tunnel insulating film, a first magnetic layer formed on one of the planes of the tunnel insulating film, a second magnetic layer formed on the other plane of the tunnel insulating film, a third magnetic layer containing an anti-ferromagnetic substance for fixing magnetization of the second magnetic layer, a second insulating film formed on at least one of the first and third magnetic layers and having an opening in a predetermined region, a first electrode electrically connected to one of the first and third magnetic layers only in the opening of the second insulating film, and a second electrode for causing a current to flow between the first electrode and itself through at least the first and second magnetic layers and the first insulating layer.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to a magnetic sensor, and moreparticularly to a magnetic head and a magnetic memory used for computersand information processing units.

2. Description of the Related Art

Magnetic recording media have been predominantly magnetic disks andmagnetic tapes. They are manufactured by forming a thin magnetic film onan Al substrate or a resin tape. A magnetic head utilizing anelectromagnetic conversion operation is used in order to write and readmagnetic information to and from these magnetic media. This magnetichead comprises a write portion for writing the magnetic information tothe recording medium and a read portion for reading out the magneticinformation from the recording medium. A so-called “induction typehead”, which comprises a coil and magnetic poles that wrap the coil fromabove and below and are electrically connected to the coil, is generallyused for the write portion. Magneto-resistance effect (MR) heads havebeen proposed recently for the read portion so as to cope with themagnetic information having a high recording density. Among the MRheads, those heads which utilize the gigantic magneto-resistance effect(GMR) are well known nowadays.

Recently, a magnetic sensor using a ferromagnetic tunnelmagneto-resistance effect (spin tunnel magneto-resistance effect: TMR)has been proposed for a magnetic memory as described in JP-A-10-4227.This TMR can obtain a greater resistance change ratio by causing acurrent to flow in a direction of film thickness of themagneto-resistance effect film than the conventional magneto-resistanceeffect devices such as the GMRs which cause a current to flow in adirection of the main plane of the magneto-resistance effect film.

According to the construction described in JP-A-10-4227, however, anupper electrode stack 30 comprising at least a free ferromagnetic layer32 and a protective layer 34 must be formed inside a contact holedefined in an insulating layer 40. Therefore, production is difficult,and film quality and film thickness of each layer inside the contacthole are likely to fluctuate from a desired level.

SUMMARY OF THE INVENTION

In view of the problems described above, the present invention aims atproviding a construction of a magnetic sensor using a spin tunnelmagneto-resistance effect (TMR) which construction can be manufacturedmore easily than the prior art devices and can stably keep film qualityand thickness at a desired level, and a method of producing the magneticsensor.

To accomplish the object, a spin tunnel magneto-resistance effectmagnetic sensor according to the present invention comprises a firstinsulating film which allows a current to tunnel and flow therethrough,a first magnetic layer formed on a first surface of the first insulatingfilm and containing a ferromagnetic substance, a second magnetic layerformed on a second surface of the first insulating film and containing aferromagnetic substance, a third magnetic layer formed on the secondmagnetic layer and containing an anti-ferromagnetic substance for fixingmagnetization of the second magnetic layer, a second insulating filmformed on at least one of the first and third magnetic layers and havingan opening in a predetermined region, a first electrode electricallyconnected to one of the first and third magnetic layers only inside theopening of the second insulating film, and a second electrode forcausing a current to flow between at least one of the first and secondmagnetic layer and the first electrode through the first insulatingfilm.

A method of producing a spin tunnel magneto-resistance effect typemagnetic sensor having a first magnetic layer containing a ferromagneticsubstance, a second magnetic layer containing a ferromagnetic substanceand a third magnetic layer containing an anti-ferromagnetic substancefor fixing magnetization of the second magnetic layer according to thepresent invention comprises the steps of (a) forming the third magneticlayer over a substrate by sputtering, (b) forming the second magneticlayer on the third magnetic layer by sputtering, (c) processing at leastthe second and third magnetic layers into a first pattern, (d) forming afirst insulating film, which allows an electric current to tunnel andflow therethrough, on at least the first pattern, by sputtering, (e)forming a first magnetic layer on the first insulating film bysputtering, (f) processing at least the first magnetic layer and thefirst insulating film into a second pattern, (g) forming a secondinsulating film in at least a predetermined region of the secondpattern, (h) forming an opening in a predetermined region of the secondinsulating film and (i) forming a first electrode, which is electricallyconnected to the first magnetic layer only inside the opening of thesecond insulating film, and forming a second electrode electricallyconnected to the second magnetic layer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing a magnetic head according to afirst embodiment of the present invention;

FIG. 2 is a sectional view showing a part of the magnetic head accordingto the first embodiment of the present invention;

FIG. 3 is a sectional view showing a part of a magnetic head accordingto a second embodiment of the present invention;

FIG. 4 is a sectional view showing a part of a magnetic head accordingto a third embodiment of the present invention;

FIG. 5 is a sectional view showing a part of a magnetic head accordingto a fourth embodiment of the present invention;

FIG. 6 is a sectional view showing a part of a magnetic head accordingto a fifth embodiment of the present invention;

FIG. 7 is a sectional view showing a part of a magnetic head accordingto a sixth embodiment of the present invention;

FIG. 8 is a sectional view showing a part of a magnetic head accordingto a seventh embodiment of the present invention;

FIG. 9 is a sectional view showing a part of a magnetic head accordingto an eighth embodiment of the present invention;

FIG. 10 is a perspective view showing a magnetic recording/reproducingapparatus using the magnetic head according to the embodiments of thepresent invention;

FIGS. 11A to 11G are sectional views each showing a production step ofthe magnetic head shown in FIG. 4;

FIGS. 12A to 12G are sectional views each showing a production step ofthe magnetic head shown in FIG. 8;

FIG. 13 is a sectional view showing a magnetic memory according to oneembodiment of the present invention; and

FIG. 14 is a plan view showing the magnetic memory according to oneembodiment of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Several embodiments of the present invention, wherein a magnetic sensoraccording to the present invention is applied to a reproducing magnetichead, will be explained initially.

The recording/reproducing head used in the first embodiment includes areproducing TMR head utilizing a TMR (spin tunnel magneto-resistanceeffect) and an induction type recording thin film magnetic head. Thereproducing TMR head is mounted onto a substrate, and the recording thinfilm magnetic head is mounted onto the TMR head.

This embodiment employs the construction for preventing a currentflowing through a magneto-resistance effect film of the reproducing TMRhead from leaking to a magnetic domain control layer, and improvesdetection efficiency of a resistance change ratio of themagneto-resistance effect film. Also, this embodiment reduces the widthof the region, in which the current of the magneto-resistance effectfilm flows, by reducing the width of electrodes which are in contactwith the magneto-resistance effect film, and reduces a track width, too.In this way, this embodiment provides a reproducing TMR head capable ofcoping with a magnetic recording medium having a higher recordingdensity.

The construction of the reproducing TMR head according to the firstembodiment will be explained more concretely with reference to FIGS. 1and 2. The recording thin film magnetic head is disposed insuperposition with the reproducing TMR head. The explanation of theconstruction of this thin film magnetic head will be omitted herebybecause it is well known in the art.

A lower shield film 10 is formed on a ceramic substrate 31 as shown inFIG. 1. An electrode film 8 patterned into a desired shape is disposedon the lower shield film 10. A magneto-resistance effect film 20 havinga four-layered structure is disposed on and at a part of the electrodefilm 8. Magnetic domain control films 7 are arranged on both sides ofthe magneto-resistance effect film 20 and an insulating film 6 isdisposed on the magneto-resistance effect film 20 and the magneticdomain control films 7 in such a fashion as to bury them. As shown inFIG. 2 which is a sectional view taken along a line A—A' of FIG. 1, athrough-hole (opening) 21 is bored in the insulating film 6 at aposition which is situated on the magneto-resistance effect film 20. Anelectrode film 5 is arranged on the insulating film 6 and keeps contactwith the magneto-resistance effect film 20 at only the through-holeportion 21. Therefore, when a current is caused to flow from theelectrode film 5 to the electrode film 8, this current flows from theportion, at which the electrode film 5 is in contact with themagneto-resistance effect film 20, to the magneto-resistance effect film20 in the direction of film thickness. Consequently, the width of theregion of the magneto-resistance effect film 20, in which the currentflows, is limited substantially to the width of the through-hole 21 andthis width practically serves as a track width. Incidentally, an uppershield film 9 (not shown in FIG. 1) is disposed on the electrode film 5.The shield films 9 and 10 are disposed in order to magnetically shield aleakage flux from the recording medium and to improve spatial resolutionof the reproducing head.

The magneto-resistance effect film 20 has the four-layered structurecomprising a ferromagnetic free layer 3, an electrical insulating layer1, a ferromagnetic fixing layer 2 and an anti-ferromagnetic layer 4 thatare laminated in order named. The free layer 3 and the fixing layer 2are formed in such a fashion that their axes of easy magnetization areparallel. Magnetization of the fixing layer 2 is fixed to apredetermined direction due to its magnetic exchange/coupling with theanti-ferromagnetic film 4. When the reproducing TMR head opposes themagnetic recording medium, magnetization of the free layer 3 rotates inaccordance with the direction of magnetization of the magneticinformation recorded on the magnetic recording medium. Therefore, thedirection of magnetization of the free layer 3 is parallel, oranti-parallel, to the direction of magnetization of the fixing layer 2.When the current is caused to flow through the magneto-resistance effectfilm 20 in the direction of film thickness through the electrode films 5and 8, the current flows while tunneling through the insulating film 1.The electric resistance of the magneto-resistance effect film 20 changesdepending on whether the directions of magnetization of the free layer 3and the fixing layer 2 are parallel or anti-parallel to each other, dueto the spin tunnel magneto-resistance effect (TMR). In other words, thetunnel current changes depending on the relative direction of the spinof magnetization in the free layer 3 and in the fixing layer 2. Therecorded signal can be reproduced by detecting this change.

The magnetic domain control film 7 is a ferromagnetic film for applyinga bias magnetic field to the free layer 3 in order to restrict theoccurrence of the magnetic domain of the free layer 3. This embodimentemploys the positional relationship such that the upper surface of eachmagnetic domain control film 7 is always positioned below the uppersurface of the insulating layer 1 (on the side of the substrate 31 shownin FIG. 1) and that the fixing layer 2 and each magnetic domain controlfilm 7 are out of mutual contact. Because the magnetic domain controlfilm 7 has a low resistivity, a part of the current flowing from theelectrode film 5 to the electrode film 8 will leak from the fixing layer2 to the electrode film 8 through the magnetic domain control film 7without tunneling through the insulating film 1 if the magnetic domaincontrol film 7 keeps contact with the fixing layer 2. The constructionshown in FIG. 2 can prevent the leak of the current because the fixinglayer 2 and the magnetic domain control films 7 are out of mutualcontact.

Next, the material of each part will be explained. The lower shield film10 is made of Co type amorphous alloys such as CoNbZr, NiFe alloys,FeAlSi alloys or CoNiFe alloys. The film thickness is from 1 to 5 μm.The upper shield film 9 is made of NiFe alloys or CoNiFe alloys and theabsolute value of its magneto-restriction constant is not greater than5×10⁻⁶. The upper shield film 9 can be used also as the lower core ofthe recording thin film magnetic head and in this case, the upper shieldfilm 9 may be a multi-layered film comprising a ferromagnetic layer andan oxide, or a ferromagnetic alloy film that contains a metalloid suchas B or P. In addition, the upper shield film 9 preferably has a highresistivity (at least 40 μΩ·cm) so as to improve high frequencycharacteristics of the recording thin film magnetic head.

Since the electrode film 8 serves as the base film of themagneto-resistance effect film 20, it must be an electrode film whichstabilizes the characteristics of the magneto-resistance effect film 20and provides a high resistance change amount. More concretely, thesurface of the electrode film 8 is preferably flat and clean and when ahigh current density is taken into consideration, the electrode film 8is preferably made of a material having a high melting point. Therefore,the electrode film 8 is formed by sputtering or vacuum deposition ofthose elements, as low resistivity materials, which have a high eltingpoint but exhibit low exothermy, such as Ta, Nb, Ru, Mo, Pt, Ir, etc,alloys containing these elements, such as Ta alloys, TaW alloys, oralloys of W, Cu, Al, and so forth. The thickness of the electrode film 8is from 3 to 30 nm and is changed in accordance with the spacing betweenthe shield film 10 and the shield film 9. The smaller the thickness ofthe electrode film 8, the smaller becomes the spacing between the shieldfilm 10 and the shield film 9, and the higher becomes resolution of thereproducing TMR head. This electrode film 8 may be a multi-layered film(e.g. a multi-layered structure of Ta layer/Pt layer/Ta layer or Talayer/Cu layer/Ta layer).

The electrode film 5 may be made of the same material as that of theelectrode film 8.

The free layer 3 of the magneto-resistance effect film 20 may have asingle layered structure made of a ferromagnetic material such as a NiFealloy, a Co alloy, a FeCo alloy or a CoNiFe alloy, or a multi-layeredstructure containing a ferromagnetic layer for preventing diffusion onthe interface or restricting anisotropic dispersion. Examples of themulti-layered structure include a structure of Co layer/NiFe layer/Colayer and a multi-layered structure of a Co layer/NiFe alloy layer/CoFelayer. Which material is used for the free layer 3 and whether the freelayer 3 uses the single layer structure or the multi-layered structureare determined also by the combination with the electrode film 8 as thebase. The fixing layer 2 can be made of Co or a Co alloy, or may be madeof the same material or may have the same structure, as that of the freelayer 3. The fixing layer 2 may also comprise a multi-layered structureof a magnetic layer(s) and a nonmagnetic layer(s). For example, it maycomprise a multi-layered structure of ferromagnetic layer/nonmagneticlayer/Co layer such as Co layer/Ru layer/Co layer. Theanti-ferromagnetic layer 4 may be made of IrMn, CrMn type alloys (suchas CrMnPt, CrMnRu and CrMnRh), MnRh alloys, MnPt alloys, MnPtPd alloys,NiMn alloys, NiMnPd alloys, MnRhRu alloys, NiO, CoO alloys, Fe₂O₃ andFe₃O₄ alloys and a CrAl alloy. Alternatively, the anti-ferromagneticfilm 4 may comprise a multi-layered film made of the combination ofthese materials. The film thickness is 3 to 10 nm for the free layer 3,1 to 10 nm for the fixing layer 2 and 2 to 25 nm for theanti-ferromagnetic film 4. These films can be formed by sputtering.

The insulating layer 1 of the magneto-resistance effect film 20 is madeof any of an oxide, a nitride, a fluoride and a boride, or a materialcontaining any of them. For example, it is made of Al₂O₃, SiO₂, Ta₂O₅,TiO₂ or an oxide having a perovskite structure, or a mixed phase of anyof these oxides, to which nitrogen is partly added, and a nitride. Theinsulating layer 1 may be a multi-layered film. The thickness of theinsulating layer 1 is extremely small, for example, 0.2 to 3 nm.

On the other hand, the insulating film 6 is made of Al₂O₃ or SiO₂. Aninsulating film having a high dielectric withstand voltage can beobtained by employing a multi-layered structure of a non-magnetic metalfilm/oxide film/non-magnetic metal film or a ferromagnetic metalfilm/oxide film/ferromagnetic metal film. For example, the insulatingfilm 6 may have a multi-layered structure of an Al film/Al₂O₃ film/Alfilm and a multi-layered structure of a Ni film/NiO film/Ni film or a Cofilm/CoO film/Co film. The insulating film 6 can be made of an oxidecontaining at least one of Ti, Sr and Ba. Among them, the filmcontaining Ti, Sr or Ba becomes a film containing the perovskitestructure and can improve the dielectric withstand voltage.

The magnetic domain control film 7 comprises a Co type hardferromagnetic film. A film of Cr, Nb or Ta as a non-magnetic metal maybe disposed as the base of the magnetic domain control film 7.

Incidentally, the width of the through-hole 21 of the insulating film 21is preferably as small as possible because it determines the trackwidth. The production process for this purpose may be as follows, forexample. The lower shield film 10 and the magneto-resistance effect film20 are formed first on the substrate 31. After the magneto-resistanceeffect film 20 is etched by milling method, the magnetic domain controlfilms 7 are then formed. The magnetic domain control films 7 formed onthe magneto-resistance effect film 20 are removed by lift-off. Theinsulating film 6 is formed. It is formed by sputtering or CVD. Next,this insulating film 6 is etched by RIE (Reactive Ion Etching) and thethrough-hole 21 is formed. The etching condition at this time is ofimportance. Namely, a CHF₃ or chlorine gas is used for etching so thatthe width of the through-hole 21 becomes small. After the electrode film5 is formed, the through-hole 21 is filled with this electrode film 5.The surface of the electrode film 5 is processed into a flat surface byetching or CMP (Chemical Mechanical Polishing) and the upper shield film9 is formed by sputtering or plating on this flat electrode film 5.Thereafter, the recording thin film magnetic head is formed on the uppershield film 9.

Next, the explanation will be given on the reproducing operation of themagnetic information of the recording medium by using the reproducingTMR head having the construction shown in FIGS. 1 and 2. First, thefloat-up surface 32 of the magneto-resistance effect head is caused tofloat above the recording medium so that the float-up surface 32 and therecording medium oppose each other with a small spacing between them.The direction of magnetization of the fixing layer 2 does not changebecause it is fixed by magnetic exchange/coupling with theanti-ferromagnetic film 4. On the other hand, magnetization of the freelayer 3 rotates with the direction of magnetization of the magneticinformation of the recording medium. In consequence, the direction ofmagnetization of the fixing layer 2 and the direction of magnetizationof the free layer 2 are either parallel or anti-parallel to each otherdepending on the magnetic information of the recording medium. When thecurrent is caused to flow between the electrode films 5 and 8, thecurrent flows in the direction of film thickness while tunneling throughthe insulating layer 1 of the magneto-resistance effect film 20. Theelectric resistance of the magneto-resistance effect film 20 at thistime varies depending on whether the direction of magnetization of thefixing layer 2 and that of the free layer 3 are parallel oranti-parallel, due to the spin tunnel magneto-resistance effect. Thismeans that the magnetic information of the recording medium can bereproduced by detecting the current between the electrode films 5 and 8and by detecting the resistance change ratio. Incidentally, when themagnetic information is recorded to the recording medium, theinformation is recorded by the recording thin film magnetic head mountedonto the reproducing TMR head by floating the float-up surface 32 overthe recording medium.

In the reproducing TMR head of the first embodiment described above, thewidth of the electrode film 5, which is in contact with themagneto-resistance effect film 20, is decreased by the insulating film 6and the track width is set to a width smaller than that of themagneto-resistance effect film 20. Therefore, the track width can benarrowed easily without reducing the width of the magneto-resistanceeffect film 20 and the recording density of the magnetic disk of themagnetic recording/reproducing apparatus can be increased.

Since the magnetic domain control film 7 and the fixing layer 2 have thepositional relationship such that they are out of mutual contact, itbecomes possible to prevent the current from leaking from the fixinglayer 2 to the electrode film 8 through the magnetic domain control film7. Since the current flowing through the magneto-resistance effect film20 in the direction of film thickness can be increased in this way, thequantity of the current that contributes to the detection of theresistance change ratio of the magneto-resistance effect film 20 due tothe spin tunnel magneto-resistance effect increases, and detectionefficiency of the resistance change ratio can be improved.

As described above, the first embodiment can provide a reproducing TMRhead which can cope with a high recording density and moreover, has highdetection efficiency of the resistance change ratio.

Next, a reproducing TMR head according to the second embodiment will beexplained with reference to FIG. 3.

In FIG. 3, like reference numerals are used to identify like layers andlike films having the same functions as in FIG. 2. A large difference ofthe reproducing TMR head shown in FIG. 3 from the reproducing head ofFIG. 2 resides in that both end portions of the magneto-resistanceeffect film 20 are so arranged as to hang on the magnetic domain controlfilms 7. According to this construction, the insulating layer 1 alwaysexists between the free layer 2 and the magnetic domain control films 7,so that the leakage current from the free layer 2 to the magnetic domaincontrol films 7 can be prevented more effectively. Therefore, themagnetic domain control films 7 can be composed of a film having a lowresistivity (CoCr alloy film). In the construction shown in FIG. 3, theupper shield film 9 is used also as the upper electrode film 5, and theproduction process can be simplified eventually.

When the insulating film 6 is made of SiO₂ and the through-hole 21 isformed by RIE using CHF₃ as the etching gas in the construction shown inFIG. 3, the width (track width) of the through-hole 21 that can beformed is from 0.2 to 0.3 μm. This track width can achieve a highrecording density of 20 Gb/in² or more.

Next, a reproducing TMR head according to the third embodiment will beexplained with reference to FIG. 4.

In FIG. 4, like reference numerals are used to identify like layers andlike films having the same functions as the layers and the films shownin FIG. 2. As shown in FIG. 4, the magneto-resistance effect film 20 istapered on the side surface at a taper angle of 50 to 80 degrees. Thistaper is generated by the incidence conditions of the ions for millingthe magneto-resistance effect film 20. The lower shield film 10 is a Cotype amorphous alloy film or a FeAlSi alloy film. The electrode film 8is made of a Ta alloy, a TaW alloy, alloys of Nb, Mo, W, Cu and Al, oralloys of precious metals such as Ru, Pt, etc. The electrode film 8comprises a multi-layered film (e.g. Ta layer/Pt layer/Ta layer or Talayer/Cu layer/Ta layer). The free layer 2 is a multi-layered film inorder to prevent diffusion on the interface or to restrict anisotropicdispersion. It has, for example, a multi-layered structure of a Colayer/NiFe layer/Co layer.

Next, a production process of the reproducing head shown in FIG. 4 willbe explained with reference to FIGS. 11A to 11G.

To begin with, the lower shield film 10 is formed on a substrate(similar to the substrate 31 shown in FIG. 1) by sputtering or plating,and then the electrode film 8 is formed by vacuum deposition. After thesurface of the electrode film 8 is subjected to ion cleaning, the freelayer 3, the insulating layer 1, the fixing layer 2 and theanti-ferromagnetic film 4 of the magneto-resistance effect film 20 areformed in order. These four layers of the magneto-resistance effect film20 are processed by ion milling. After the resist film 12 having theshape shown in FIG. 11A is formed on the magneto-resistance effect film20 which is so processed, the magnetic domain control films 7 are formed(FIG. 11B), the resist film 12 is dissolved, and the magnetic domaincontrol films 7 on the magneto-resistance effect film 20 are lifted off(FIG. 11C). The insulating film 6 is then formed, and then the resistfilm 13 is formed on this insulating film 6 and is patterned (FIG. 11D).Next, the insulating film 6 is processed by IRE using the resist film 13as a mask. This process step forms the through-hole 21 (FIG. 11E).Incidentally, a stopper film may be formed in advance between theanti-ferromagnetic film 4 and the insulating film 6 in order to preventthe anti-ferromagnetic film 4 from being damaged by RIE. The resist film13 is removed (FIG. 11F) and the upper shield film 9 is formed on theinsulating film 6 (FIG. 11G). In this way, the reproducing TMR headshown in FIG. 4 can be produced.

Incidentally, the upper shield film 9 shown in FIGS. 3 and 4 serves alsoas the electrode film 5 but in this case, the upper shield film 9 is notsmooth and flat in comparison with the construction of FIG. 1 becausethe upper shield film 9 has the shape that profiles the insulating film6 and the magneto-resistance effect film 20. Therefore, magnetic wallsare likely to be defined on the upper shield film 9 in the proximity ofthe through-hole 21. To prevent the formation of the magnetic walls, anon-magnetic film may be formed in the proximity of the through-hole 21as a multi-layered shield film 9. It has been found that the formationof the magnetic walls can be prevented by forming, for example, a shieldfilm 9 having a multi-layered structure comprising a NiFe layer/Al₂O₃layer/NiFe layer, and the shield film 9 contributes to the prevention offluctuation of the output of the reproducing TMR head and the occurrenceof the noise.

Next, a reproducing TMR head according to the fourth embodiment will beexplained with reference to FIG. 5.

In FIG. 5, like reference numerals are used to identify like layers andfilms having the same functions as those shown in FIG. 2. In thereproducing TMR head shown in FIG. 5, the magneto-resistance effect film20 is tapered, the free layer 3 inside the magneto-resistance effectfilm 20 has a greater width than the other layers 1, 2 and 4, and theinsulating film 6 is so arranged as to be in contact with both ends ofthe upper surface of the free layer 3. In comparison with theconstruction shown in FIG. 4, the construction of FIG. 5 completelyisolates the magnetic domain control films 7 and the fixing layer 2 bythe insulating film 6, and can prevent with high reliability the leak ofthe current from the fixing layer 2 to the magnetic domain control films7.

When the reproducing TMR head shown in FIG. 5 is produced, only the freelayer 3 of the magneto-resistance effect film 20 is first formed andthen milling is effected once so as to process only the free layer 3.Thereafter, the three layers of the insulating layer 3, the fixing layer2 and the anti-ferromagnetic film 4 are formed and milling is carriedout once again to process these three layers. Alternatively, the fourlayers of the magneto-resistance effect film 20 are formed all at once,the three layers of the insulating layer 3, the fixing layer 2 and theanti-ferromagnetic film 4 are then etched by milling and etching isstopped on the free layer 3. In either case, the shape shown in FIG. 5can be accomplished. Other production steps and the materials may be thesame as those of the embodiment shown in FIG. 4.

Next, FIGS. 6 to 9 show the fifth to eighth embodiments wherein a highresistivity film 11 is interposed between the magnetic domain controlfilms 7 and the magneto-resistance effect film. This high resistivityfilm 11 is to prevent the current flowing through the magneto-resistanceeffect film 20 in the direction of film thickness from leaking to themagnetic domain control films 7, and is made of an insulating materialor a semiconductor.

The construction of the reproducing TMR shown in FIG. 6 seems analogousto the construction shown in FIG. 4, but it is not equipped with theinsulating film 6 but is equipped instead with the high resistivity film11. The high resistivity film 11 is disposed in such a fashion as tocover the side surface of the magneto-resistance effect film 20 and themagnetic domain control layers 7 are disposed outside the highresistivity film 11. The through-hole is bored in the high resistivityfilm 11 in the same way as in the case of the insulating film 6 shown inFIG. 4 and the width of this through-hole determines the width of theelectrode film 5 (serving also as the upper shield film 9) which is incontact with the anti-ferromagnetic film 4, that is, the track width.

The procedure for producing the reproducing TMR head shown in FIG. 6will be explained briefly. First, the lower shield film 10, theelectrode film 8 and the magneto-resistance effect film 20 are formedserially on the substrate 31 and then the magneto-resistance effect film20 is processed by miling. The high resistivity film 11 is formed on themagneto-resistance effect film 20 by sputtering SiO₂ or Al₂O₃ to a filmthickness of 5 to 10 nm. The adhering condition of the film is adjustedby changing the sputtering condition (particularly, the distance betweenthe substrate and the target) and the high resistivity film 11 havingthe thickness shown in FIG. 6 is formed. Next, the magnetic domaincontrol films 7 are formed. The thickness of the magnetic domain controlfilms 7 is 5 to 20 nm. The magnetic domain control films 7 on themagneto-resistance effect film 20 are removed by lift-off in the sameway as in FIGS. 11B and 11C. The through-hole is formed in the highresistivity film 11 by the same means as the one shown in FIGS. 11D to11F. Thereafter the upper shield film 9 (serving also as the electrodefilm 5) is formed.

On the other hand, each of the constructions shown in FIGS. 7 to 9 isequipped with both the insulating film 6 and the high resistivity film11. The film thickness of the high resistivity film 11 is large at theupper portion of the side surfaces of the magneto-resistance effect film20 but is uniform at other flat portions. The upper surface of eachmagnetic domain control film is flat and is in conformity with the uppersurface of the magneto-resistance effect film 20. Therefore, theinsulating film 6 has a uniform thickness. Further, the order of eachlayer of the magneto-resistance effect film 20 is exactly opposite tothe order of the constructions shown in FIGS. 2 to 6. In other words,the anti-ferromagnetic film 4, the fixing layer 2, the insulating layer1 and the free layer 3 are disposed in order named from the electrodefilm (8) side. The track width is determined by the spacing of thethrough-hole of the insulating film 6 in entirely the same way as in theconstructions shown in FIGS. 2 to 5.

In the construction shown in FIG. 8, the lower electrode film 8 (servingalso as the base film of the magneto-resistance effect film 20), too, isprocessed by milling and the high resistivity film 11 is formed on theside surface portion of the electrode film 8, too. In the constructionshown in FIG. 9, the high resistivity film 11 extends up to both endportions of the upper surface of the free layer 3.

The production process of the reproducing TMR head having theconstruction shown in FIG. 8 will be explained with reference to FIGS.12A to 12G.

Initially, the lower shield film 10 is formed by sputtering or platingon the substrate (similar to the substrate 31 shown in FIG. 1) and theelectrode film 8 is formed by vacuum deposition. After the surface ofthe electrode film 8 is cleaned by ion cleaning, the anti-ferromagneticfilm 4, the fixing layer 2, the insulating layer 1 and the free layer 3of the magneto-resistance effect film 20 are serially formed. These fourlayers of the magneto-resistance effect film 20 and the electrode film 8are then processed by ion milling. A resist film 42 having the shape oftwo stages as shown in FIG. 12A is formed on the magneto-resistanceeffect film 20 so processed. The high resistivity film 11 is formed onthis resist film 42 (FIG. 12B). The resist film 42 is dissolved and thehigh resistivity film 11 on the magneto-resistance effect film 11 islifted off. The magnetic domain control films 7 are formed next. Theupper surface of the magnetic domain control films 7 is polished to aflat surface by CMP (Chemical Mechanical Polishing) (FIG. 12D). Theinsulating film 6 and the resist film 43 are serially formed on thiscontrol film 7 and the resist film 43 is patterned (FIG. 12E). Theinsulating film 6 is processed by RIE using this resist film 43 as themask. In this way the through-hole 21 can be formed (FIG. 12F). Afterthe resist film 43 is removed, the upper shield film 9 (which servesalso as the electrode film 5) is formed on the insulating film 6 (FIG.12G). As a result, the reproducing TMR head shown in FIG. 8 can befabricated.

In the reproducing TMR head having each of the constructions shown inFIGS. 6 to 9, the high resistivity film 11 covers the entire sidesurface of the magneto-resistance effect film 20 and electricallyisolates the magnetic domain control films 7 from the magneto-resistanceeffect film 20. Therefore, the leakage current flowing from the fixinglayer 2 to the electrode film 8 through the magnetic domain control film7 does not occur, and the current flowing through the magneto-resistanceeffect film 20 in the direction of film thickness can be increased. Inconsequence, detection efficiency of the resistance change ratio of themagneto-resistance effect film 20 due to the spin tunnelmagneto-resistance effect can be improved.

The constructions shown in FIGS. 6 to 9 reduce the width of theelectrode film 5, which is in contact with the magneto-resistance effectfilm 20, to a smaller width than the width of the insulating film 6 andthe high resistivity film 11 so that the track width becomes smallerthan the width of the magneto-resistance effect film 20, in the same wayas the constructions shown in FIGS. 2 to 4. Therefore, the track widthcan be easily made narrower without reducing the width of themagneto-resistance effect film 20 and the recording density of themagnetic disk of the magnetic recording/reproducing apparatus can beincreased.

Further, in the constructions shown in FIGS. 7 to 9, the upper surfaceof the magnetic domain control films 7 is brought into conformity withthe upper surface of the magneto-resistance effect film 20 and isrendered flat. Therefore, the upper shield film 9 (serving also as theelectrode film 5) can keep a uniform thickness with the exception of theportion of the through-hole 21. For this reason, the magnetic wall doesnot easily develop in the upper shield film 9 and performance of theupper shield film 9 can be improved.

Next, the overall construction and operation of a magneticrecording/reproducing apparatus using the reproducing TMR head of eachembodiment of the present invention described above will be explainedwith reference to FIG. 10.

A recording/reproducing head 210 includes the reproducing TMR head inany of the constructions shown in FIGS. 2 to 9 and a recording thin filmmagnetic head mounted onto the reproducing TMR head. Therecording/reproducing head 210 is supported at the distal end of aspring 211 with its float-up surface facing down. The spring is fittedto a head positioning mechanism 320. The head positioning mechanism 320positions the recording/reproducing head 210 onto a recording medium(hard disk) 110. The recording medium 110 is driven for rotation by aspindle motor 310. When recording is made, the inputted recording datais encoded by an encoder 335 and a recording current is supplied by arecording amplifier 336 to the recording thin film magnetic head. Whenreproduction is made, on the other hand, the current flowing between theelectrode films 5 and 8 of the reproducing TMR head is processed by asignal processing system 330 and the magnetic information of therecording medium 110 is reproduced. More concretely, the current flowingbetween the electrode films 5 and 8 is amplified by a pre-amplifier 331and the data is reproduced by a data reproducing circuit 332 and isdecoded by a decoder 333. A servo detector 334 controls tracking of therecording/reproducing head 210 by using the output signal of thepre-amplifier 331. A controller 340 controls the signal processingoperations described above.

The magnetic recording/reproducing apparatus shown in FIG. 10 isequipped with the TMR head having any of the constructions of theembodiments of the present invention shown in FIGS. 2 to 9 as thereproducing head of the recording reproducing apparatus. Since this TMRhead can prevent the leak of the current to the magnetic domain controlfilm 7, the signal processing system 330 can detect with high efficiencythe resistance change ratio due to the spin tunnel magneto-resistanceeffect, and a magnetic recording/reproducing apparatus having a highdetection sensitivity at the time of reproduction can be obtained. Sincethe width of the electrode film 5 which is in contact with themagneto-resistance effect film 20 is reduced in this TMR head, the trackwidth is small and the magnetic information of the recording medium 110recorded in a high recording density can be reproduced.

In this way, the embodiments of the present invention can provide theconstruction of the recording/reproducing head using the spin tunnelmagneto-resistance effect which head can prevent the leakage current andmoreover has a small track width and high practicality, and the magneticrecording/reproducing apparatus using the recording/reproducing head.

Next, an embodiment wherein the magnetic sensor according to the presentinvention is applied to a magnetic memory will be explained.

FIG. 13 is a sectional view showing a magnetic memory according to thisembodiment and FIG. 14 is a plan view showing the magnetic memoryaccording to this embodiment. A first base layer 42, a second base layer43, an anti-ferromagnetic layer 44 and a fixing layer 45 are formed bysputtering, or the like, on a substrate 41. These layers are etched intoa first pattern extending in a first direction. Next, an insulatinglayer 46, a free layer 47 and a third base layer 48 are formed bysputtering, or the like. These layers are etched into a second pattern.The anti-ferromagnetic layer 44, the fixing layer 45, the insulatingfilm 46 and the free layer 47 together constitute a magneto-resistanceeffect film 60 in a region where the first pattern and the secondpattern cross each other. Next, an insulating film 49 is formed andpatterned around the crossing region of the first and second patterns,and an opening 61 is formed at a substantial center of the insulatingfilm 49. An upper electrode 50 is formed on the insulating film 49inclusive of the inside of the opening 61. The upper electrode 50defines a third pattern extending in a second direction crossingorthogonally the first direction and is electrically connected to thefree layer 47 through the third base layer 48 only inside the opening 61of the insulating film 49. Further, a first lower electrode 51 and asecond lower electrode 52 are formed and patterned on a predeterminedregion of the fixing layer 45.

When a current is caused to flow between the first and second lowerelectrodes in the construction described above, the current flowsthrough at least the fixing layer 45, and the direction of magnetizationof the free layer 47 is determined by the flowing direction of thecurrent, so that the data is stored. The magnetic characteristics of theanti-ferromagnetic layer 44 for fixing magnetization of the fixing layer45 are decided so that the direction of magnetization of the free layer47 is parallel or anti-parallel to the direction of magnetization of thefixing layer 45. When the current is caused to flow in the direction offilm thickness of the magneto-resistance effect film 60 by applying avoltage between the upper electrode 50 and the first lower electrode 51or between the upper electrode 50 and the second lower electrode 52, thecurrent flows while tunneling through the insulating film 46, and theelectric resistance of the magneto-resistance effect film 60 changesdepending on whether the directions of magnetization of the free layer47 and the fixing layer 45 are parallel or anti-parallel to each other,due to the spin tunnel magneto-resistance effect (TMR). The data that isstored can be read out by detecting this change. Though this embodimentuses a RAM (Random Access Memory) construction capable of writing thedata, a ROM (Read-Only Memory) construction can be employed, too, byomitting the second lower electrode 52. When the ROM construction isemployed, the data may be stored in advance by applying the magneticfield from outside.

Next, the material of each part will be explained. Silicon or ceramics,for example, can be used for the substrate 41. Tantalum (Ta), forexample, can be used for the first base layer 42 and the third baselayer 48. A NiFe alloy, for example, can be used for the second baselayer 43. A FeMn alloy or a MnIr alloy, for example, can be used for theanti-ferromagnetic layer 44. A CoFe alloy, for example, can be used forthe fixing layer 45. Al₂O₃, for example, can be used for the insulatingfilms 46 and 49. A CoFe alloy or a NiFe alloy, for example, can be usedfor the free layer 47. Gold (Au), copper (Cu), tantalum (Ta), ruthenium(Ru), etc, for example, can be used for the upper electrode 50, thefirst lower electrode 51 and the second lower electrode 52. In addition,those materials which are described as usable for respective portions inthe description of the foregoing embodiments of the magnetic heads maybe employed, as well.

As described above, this embodiment provides the magnetic memory whichcan be produced more easily than the conventional processes and whichcan keep stably and satisfactorily film quality and film thickness ofeach layer.

What is claimed is:
 1. A spin tunnel magneto-resistance effect typemagnetic sensor comprising: a first insulating film capable of allowinga current to flow while tunneling therethrough; a first magnetic layerformed on a first plane of said first insulating film, and containing aferromagnetic substance; a second magnetic layer formed on a secondplane of said first insulating film, and containing a ferromagneticsubstance; a third magnetic layer formed on said second magnetic layer,and containing an anti-ferromagnetic substance for fixing magnetizationof said second magnetic layer; a second insulating film formed on atleast one of said first and third magnetic layers, and having an openingin a predetermined region; a first electrode electrically connected toone of said first and third magnetic layers only inside said opening ofsaid second insulating film; a second electrode for causing a current toflow between said first electrode and itself through at least said firstand second magnetic layers and said first insulating film; said firstmagnetic layer formed on a predetermined region of said secondelectrode; and a pair of magnetic domain control films, formed on bothsides of said first magnetic layer to be out of contact from said secondmagnetic layer, for applying a magnetic bias to said first magneticlayer to control the magnetic domain of said first magnetic layer.
 2. Amagnetic sensor according to claim 1, wherein: said first magnetic layeris so disposed as to hang over said pair of magnetic domain controlfilms; and said first insulating film, said second magnetic layer andsaid third magnetic layer are laminated on said first magnetic layer. 3.A magnetic sensor according to claim 1, wherein: said second insulatingfilm includes a high resistivity film covering side surfaces of saidfirst magnetic layer, said first insulating film, said second magneticlayer and said third magnetic layer; and said pair of magnetic domaincontrol films are formed on said high resistivity film.
 4. A magneticrecording/reproducing apparatus comprising: medium driving means fordriving a magnetic recording medium; a head assembly including anelectromagnetic induction type magnetic head as a recording head forrecording signals to said magnetic recording medium and said magneticsensor according to claim 1 as a reproducing head for reproducing thesignals recorded on said magnetic recording medium; head driving meansfor driving said head assembly; and signal processing means forprocessing recording signals to be applied to said recording head andreproduction signals output from said reproducing head.
 5. A spin tunnelmagneto-resistance effect type magnetic sensor comprising: a firstinsulating film capable of allowing a current to flow while tunnelingtherethrough; a first magnetic layer formed on a first plane of saidfirst insulating film, and containing a ferromagnetic substance; asecond magnetic layer formed on a second plane of said first insulatingfilm, and containing a ferromagnetic substance; a third magnetic layerformed on said second magnetic layer, and containing ananti-ferromagnetic substance for fixing magnetization of said secondmagnetic layer; a second insulating film formed on at least one of saidfirst and third magnetic layers, and having an opening in apredetermined region; a first electrode electrically connected to one ofsaid first and third magnetic layers only inside said opening of saidsecond insulating film; a second electrode for causing a current to flowbetween said first electrode and itself through at least said first andsecond magnetic layers and said first insulating film; and a pair ofdomain control films applying a magnetic bias to said first magneticlayer, a spacing between said domain control films being larger than awidth of said opening.